Materials science basics: chemical composition, structure, and properties

Materials science is a science studying the interrelation between chemical composition, structure, and properties of materials, as well as their changes under the effect of various external factors.

The main task of materials science is to find the optimal combination of material chemical composition and processing method to achieve specified properties, for example elevated strength or ductility, high electrical conductivity, and other properties. This is important for various areas, from producing metal alloys to creating polymers and composites.

Materials science covers all varieties of materials, including metals, alloys, polymers, glass, ceramics, and others. An important branch of this science is physical metallurgy, which focuses on studying the interrelation between chemical composition, structure, and properties exclusively of metals and metal alloys.

Chemical composition of metal

Chemical composition of a material is the percentage ratio of chemical elements present in it. Exactly it determines the main properties of materials. This is especially important in producing precision alloys, where accuracy of chemical composition plays a key role. For even small changes in element content can substantially affect the final product characteristics.

At PZPS a spectral laboratory operates that precisely determines chemical composition of alloys at every stage of the technological process, which makes it possible to ensure high quality of our products.

Metal structure

Structure includes full information about the material under study: from electronic structure of individual atoms to surface defects visible to the naked eye.

When studying material structure one distinguishes:

• macrostructure research — makes it possible to reveal defects (chips, cracks, pores, cavities, etc.) visible to the naked eye and at magnification of not more than 10 times (loupe);
• microstructure analysis — determining particle arrangement that can be seen only at high magnification using an optical (up to 1,000 times) or electron (up to 25,000 times) microscope.

At the same time materials may, having identical chemical composition, possess different structure and, as a consequence, various properties.

Various methods are used to study structure:

• X-ray analysis — based on the fact that, passing through normal metal structure or existing defects, X-rays are attenuated differently;
• magnetic and ultrasonic flaw detection — distortion of magnetic field intensity and ultrasonic waves makes it possible to detect internal and external defects in the structure;
• capillary flaw detection — using special liquids makes it possible to detect fine cracks invisible to the eye on the metal surface.

For controlling structure of steels and alloys at PZPS a metallographic laboratory operates. In particular, non-metallic inclusions and grain score are assessed there, which helps precisely determine properties of products released.

Material properties

Material properties can be influenced both through their chemical composition and by changing their structure in various kinds of processing.

For example, when reducing carbon amount in steel its strength decreases but ductility increases. When raising carbon amount casting properties become better, but forgeability and weldability deteriorate. Adding silicon raises alloy elasticity, and manganese — its strength.

Special influence on metal properties is exerted by pressure working, since under such action work hardening forms — grain deformation as a result of which steel strength and hardness increase. This state can be relieved or other changes introduced into the material’s internal structure by heat treatment: annealing, quenching, and tempering.

• Annealing provides for heating the material to a certain temperature, subsequent holding, and slow cooling (together with the furnace). It makes steels and alloys less hard and improves their machinability, and also relieves internal stresses.
• Quenching is heating the material to a certain temperature, holding it at this temperature, and subsequent rapid cooling (in water, oil, or other quenching media). It raises material strength and hardness but reduces its ductility and toughness.
• Tempering is heat treatment applied after quenching the material. Its purpose is to obtain a more equilibrium structure of steel or alloy and relieve internal stresses after quenching.

As a result of heat treatment mechanical properties of steel or alloy can be fully changed: by quenching and annealing one can obtain two materials with significant differences in hardness, toughness, and ductility.

Materials science is a key discipline for engineers and manufacturers making it possible to create materials with required characteristics. By controlling chemical composition and structure, and also understanding the influence of various processing methods, one can achieve optimal properties of steel or alloy while retaining high quality and production efficiency. At PZPS you can order material with exactly those properties needed for your production and be confident in product quality.